Vehicle engines provide power for a plurality of external loads such as an alternator, an A/C compressor, a power steering pump, a hydraulic pump, etc. When these loads require power, the engine, increases power output to maintain driving power, which is noticeable when the engine is idling. A noticeable dip in engine idle speed occurs when engine power is used to drive the load, which is undesirable.
Conventional engine controllers advance the spark timing of the engine to compensate for the loss in engine power and the resulting dip in idle speed. Spark advance provides a fast acting engine torque actuator that compensates for the reduced engine power and maintains constant speed. During idle, spark advance causes the engine to be less efficient. Additionally, combustion instabilities occur and difficulties are presented in misfire calibration.